DataGridView自定义组合框实现错误，共享相同的值

我认为您应该在您的TreeComboBoxCell类中添加以下内容:

public override void DetachEditingControl()
{
    var ctl = DataGridView.EditingControl as TreeComboBoxEditingControl;
    if (ctl != null)
        ctl.SelectedNodeChanged -= Ctl_SelectedNodeChanged;
    base.DetachEditingControl();
}

同时修改以下方法为:

public override void InitializeEditingControl(int rowIndex, object
    initialFormattedValue, DataGridViewCellStyle dataGridViewCellStyle)
{
    base.InitializeEditingControl(rowIndex, initialFormattedValue, dataGridViewCellStyle);
    var ctl = DataGridView.EditingControl as TreeComboBoxEditingControl;
    ctl.SetItems(Items);
    ctl.SelectedNode = initialFormattedValue != null ? ctl.AllNodes.FirstOrDefault(x => Equals(x.Tag, initialFormattedValue)) : null;
    ctl.SelectedNodeChanged += Ctl_SelectedNodeChanged;
}

也删除ValueType覆盖，让DefaultNewRowValue返回null而不是0。

但我看到的主要问题是你的单元格和编辑器类之间的同步。单元格类在Items集合中使用TreeComboBoxItem对象，但编辑器GetEditingControlFormattedValue返回一个对象，这实际上是TreeComboBoxItem.Value属性。这样基单元格类就不能正确地翻译它。我不确定你甚至应该从DataGridViewComboBoxCell继承，因为它期望在许多你不处理的覆盖ComboBox编辑器。从DataGridViewCell或DataGridViewTextBoxCell继承可能会更好，就像在MSDN示例中您的代码所基于的那样。至少您可以尝试添加以下覆盖，以使单元格类实现与当前编辑器实现匹配:

protected override object GetFormattedValue(object value, int rowIndex, ref DataGridViewCellStyle cellStyle, TypeConverter valueTypeConverter, TypeConverter formattedValueTypeConverter, DataGridViewDataErrorContexts context)
{
    if (value != null)
        foreach (TreeComboBoxItem item in Items)
            if (Equals(item.Value, value)) return item.Display;
    return base.GetFormattedValue(value, rowIndex, ref cellStyle, valueTypeConverter, formattedValueTypeConverter, context);
}
public override object ParseFormattedValue(object formattedValue, DataGridViewCellStyle cellStyle, TypeConverter formattedValueTypeConverter, TypeConverter valueTypeConverter)
{
    return formattedValue;
}

EDIT好吧，我不确定到底是什么不起作用，它可能是用法。下面是一个完整的工作代码:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace System.Windows.Forms
{
    public class TreeComboBoxItem
    {
        public object Group { get; set; }
        public object Value { get; set; }
        private string display;
        public string Display { get { return display ?? (Value != null ? Value.ToString() : null); } set { display = value; } }
    }
    public class DataGridViewTreeComboBoxColumn : DataGridViewComboBoxColumn
    {
        public DataGridViewTreeComboBoxColumn()
        {
            base.CellTemplate = new TreeComboBoxCell();
        }
        public override DataGridViewCell CellTemplate
        {
            get { return base.CellTemplate; }
            set { base.CellTemplate = (TreeComboBoxCell)value; }
        }
    }
    public class TreeComboBoxCell : DataGridViewComboBoxCell
    {
        public TreeComboBoxCell() { }
        public override Type EditType { get { return typeof(TreeComboBoxEditingControl); } }
        public override void InitializeEditingControl(int rowIndex, object
            initialFormattedValue, DataGridViewCellStyle dataGridViewCellStyle)
        {
            base.InitializeEditingControl(rowIndex, initialFormattedValue, dataGridViewCellStyle);
            var ctl = DataGridView.EditingControl as TreeComboBoxEditingControl;
            ctl.SetItems(Items);
            ctl.SelectedNode = Value != null ? ctl.AllNodes.FirstOrDefault(x => Equals(x.Tag, Value)) : null;
            ctl.SelectedNodeChanged += OnEditorSelectedNodeChanged;
        }
        public override void DetachEditingControl()
        {
            var ctl = DataGridView.EditingControl as TreeComboBoxEditingControl;
            if (ctl != null) ctl.SelectedNodeChanged -= OnEditorSelectedNodeChanged;
            base.DetachEditingControl();
        }
        public override object Clone()
        {
            var dataGridViewCell = base.Clone() as TreeComboBoxCell;
            if (dataGridViewCell != null)
            {
            }
            return dataGridViewCell;
        }
        protected override object GetFormattedValue(object value, int rowIndex, ref DataGridViewCellStyle cellStyle, TypeConverter valueTypeConverter, TypeConverter formattedValueTypeConverter, DataGridViewDataErrorContexts context)
        {
            if (value != null)
            {
                foreach (TreeComboBoxItem item in Items)
                    if (Equals(item.Value, value)) return (context & DataGridViewDataErrorContexts.Formatting) != 0 ? item.Display : value;
            }
            return base.GetFormattedValue(value, rowIndex, ref cellStyle, valueTypeConverter, formattedValueTypeConverter, context);
        }
        public override object ParseFormattedValue(object formattedValue, DataGridViewCellStyle cellStyle, TypeConverter formattedValueTypeConverter, TypeConverter valueTypeConverter)
        {
            return formattedValue;
        }
        private void OnEditorSelectedNodeChanged(object sender, EventArgs e)
        {
            var selectedNode = ((TreeComboBoxEditingControl)sender).SelectedNode;
            Value = selectedNode != null ? selectedNode.Tag : null;
        }
    }
    public class TreeComboBoxEditingControl : ComboTreeBox, IDataGridViewEditingControl
    {
        public TreeComboBoxEditingControl() { TabStop = false; }
        public DataGridView EditingControlDataGridView { get; set; }
        public int EditingControlRowIndex { get; set; }
        public bool EditingControlValueChanged { get; set; }
        public bool RepositionEditingControlOnValueChange { get { return false; } }
        public Cursor EditingPanelCursor { get { return Cursor; } }
        public void SetItems(DataGridViewComboBoxCell.ObjectCollection items)
        {
            if (Nodes.Count > 0) return;
            foreach (var group in items.Cast<TreeComboBoxItem>().GroupBy(x => x.Group))
            {
                var parent = Nodes.Add(group.Key.ToString());
                foreach (var item in group)
                    parent.Nodes.Add(item.Display).Tag = item.Value;
            }
            Sort();
        }
        protected override void OnSelectedNodeChanged(EventArgs e)
        {
            EditingControlValueChanged = true;
            EditingControlDataGridView.NotifyCurrentCellDirty(true);
            base.OnSelectedNodeChanged(e);
        }
        public object EditingControlFormattedValue
        {
            get { return GetEditingControlFormattedValue(DataGridViewDataErrorContexts.Formatting); }
            set
            {
            }
        }
        public object GetEditingControlFormattedValue(DataGridViewDataErrorContexts context)
        {
            if (SelectedNode == null) return null;
            return (context & DataGridViewDataErrorContexts.Formatting) != 0 ? SelectedNode.Text : SelectedNode.Tag;
        }
        public void ApplyCellStyleToEditingControl(DataGridViewCellStyle dataGridViewCellStyle)
        {
            BackColor = dataGridViewCellStyle.BackColor;
            ForeColor = dataGridViewCellStyle.ForeColor;
        }
        public void PrepareEditingControlForEdit(bool selectAll)
        {
        }
        public bool EditingControlWantsInputKey(Keys key, bool dataGridViewWantsInputKey)
        {
            switch (key & Keys.KeyCode)
            {
                case Keys.Left:
                case Keys.Up:
                case Keys.Down:
                case Keys.Right:
                case Keys.Home:
                case Keys.End:
                case Keys.PageDown:
                case Keys.PageUp:
                    return true;
                default:
                    return !dataGridViewWantsInputKey;
            }
        }
    }
}
namespace Tests
{
    class Parent
    {
        public string Name { get; set; }
        public override string ToString() { return Name; }
    }
    class Child
    {
        public Parent Parent { get; set; }
        public string Name { get; set; }
    }
    class TestForm : Form
    {
        public TestForm()
        {
            var parents = Enumerable.Range(1, 6).Select(i => new Parent { Name = "Parent " + i }).ToList();
            var childen = Enumerable.Range(1, 10).Select(i => new Child { Parent = parents[i % parents.Count], Name = "Child " + i }).ToList();
            var items = parents.Select((parent, i) => new TreeComboBoxItem { Value = parent, Group = "Group " + ((i % 2) + 1) }).ToArray();
            var dg = new DataGridView { Dock = DockStyle.Fill, Parent = this, AutoGenerateColumns = false };
            var c1 = new DataGridViewTreeComboBoxColumn { DataPropertyName = "Parent", HeaderText = "Parent" };
            c1.Items.AddRange(items);
            var c2 = new DataGridViewTextBoxColumn { DataPropertyName = "Name", HeaderText = "Name" };
            dg.Columns.AddRange(c1, c2);
            dg.DataSource = new BindingList<Child>(childen);
        }
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new TestForm());
        }
    }
}